Magnetic core for inductance-coils.



W. FONDI'LLER.

MAGNETlC CORE FOR INDUCTANCE COILS.

APPLICATION jlLED NOV. 20. 1914.

1 1 82, 9 9'7 Patented May 16, 1916.

W/messesf I //7 van far.

QM W/mm Fond/war.-

form of the so-called air-gap UNITED STATES PATENT OFFICE.

WILLIAM EONDILLER, OF NEW YORK, N. Y., ASSIGNOR, BY MESNE ASSIGNMENTS, TO WESTERN ELECTRIC COMPANY, INCORPORATED, A CORPORATION OF NEW YORK.

MAGNETIC CORE FOR INDUCTANCE-COILS.

cification of Letters Patent.

Patented May 16, 1916.

Application filed November 20, 1914. Serial No. 873,198.

New York, in the county of New York and State of New York, have invented certain new and useful Improvements in Magnetic Cores for Inductance-Coils, of which the following is a full, clear, concise, and exact description.

This invention relates to magnetic cores for inductance coils, and more particularly it relates to cores for loading coils such as are used, for example,-in loading telephone circuits according to the Pupin system, and its object is to provide an inexpensive core of rigid construction which will be free from the deleterious effects of residual magnetism and one to which balanced windings may easily be applied.

Loading coils of the type in question are customarily equipped with magnetic cores usually in the form of a closed toroid. While such cores are entirely satisfactory for use in loading some telephone lines such as physical cable circuits, they have an objection which develops in the loading -of phantom circuits, notably open'wire phantom circuits, in that they are then often subjected to unusual magnetizing forces, such, for example. as an excessive current flow caused by lightning discharges. In such cases a certain amount of residual magnetism is retained by a core'having a closed magnetic path. This residual magnetism alters the permeability of the loading coil core to currents of telephonic frequence,

thereby changing the inductive characteristics of the line in which said coil is included.

Vhere such a line is employed in a phantom system such an alteration of inductance is objectionable as being productive of irregularities. which interfere with the efficient operation of the system as a whole, especially if repeaters are to be employed therewith. It has been found that this danger of residual magnetism and the irregularities caused thereby may be substantially eliminated by making the magnetic core discontinuous, and it has therefore heretofore been proposed to provide such a core with one or more non-magnetic transverse gaps.

This invention provides an improved type of coil in which a series of partially transverse air-gaps are symmetrically distributed throughout the core. This results in a cor of rigid construction to which windings may be applied, and accurate electromagnetic and electrostatic balances obtained without resorting to the precautionary measures necessary in winding cores in which the air-gap isnot uniformly distributed.

In the preferred embodiment of my invention the core is formed of a plurality of thin laminae, each of which contains an air-gap. These laminae are arranged in groups in such a way that the air-gaps in a given group coincide. The groups are then stacked up to form a core, and arranged in such a way that the air-gaps of the various groups are angularly displaced with respect to each other, an arrangement which results in what is in effect a cumulative air-gap symmetrically distributed with respect to both the transverse and longitudinal dimensions of the core.

The specific features of this invention will be more clearly'understood by reference to the accompanying drawing, in which Figure 1 represents a plan view of the assembled core; Fig. 2 represents a side view of the core; Fig. 3 represents an enlarged fragmentary view of one of the groups of laminae; and Fig. at represents an arrangement of windings on such a core, whereby it is made suitable for loading a phantom circuit.

Referring more particularly to the drawings, core 5 is composed of a number of layers 6, each of which layers is composed of a number of laminations 7. Each group has a transverse air-gap 8, these air-gaps being distributed symmetrically about the core, as shown in Figs. 1 and 2. \Vhile in this-case eight layers and consequently eight air-gaps are shown, it is to be understood that any other number of layers and any number of laminations in a layer may be used, provided a symmetrical arrangement is obtained. The required core demagneti zation factor may be obtained by a suitable selection of the magnetic material of whichthe laminations 7 are composed and by proper proportions of the length of air-gap 8 and thickness of layer 6.

In the preferred arrangement herein shown, the laminations are made of silicon steel approximately .005 of an inch inthickness and are provided with an insulating tial that the windings be symmetrically distributed with respect to the different sectional air-gaps and from this it develops that the number of air-gaps should be an even multiple of the number of winding sections into which the core is divided.

In the arrangement shown in Fig. 4, conductors 10, 11, 12 and 13 represent one physical circuit of a phantom arrangement, and conductors 15, 16, 17 and 18 represent the conductors of the other physical circuit of the phantom arrangement. In accordance with the well-established method for winding phantom coils, as disclosed in the Campbell-Shaw Patent No. 980,921, January 10, 1911 conductor 10 is continued to an inner winding 20,v through said winding to an outer winding 21 on the diametrically opposed quadrant of the core, through said winding to conductor 13, Similarly, conductor 11 is connected to inner winding 22, through said winding to outer winding 23, and through said winding to conductor 12. Similarly, conductor 15 is connected to an outer winding 24, through said winding to an inner winding 25 on the diametrically opposed quadrant of the core, through said winding to conductor 17 and conductor 16 is connected to an outer winding 26, through said winding to inner winding 27, through said winding to conductor 18. It should be noted that the winding in cluded in the two conductors of the one physical circuit are located on twoquadrants diametrically opposed, and that the windings included in the conductors of the other physical circuits are located on the @opiu of this patent may he obtained for five cents each, by addressing the In applying windother two quadrants of the core, this arrangement being one which greatly lessens the possibility of unbalance between comprising'a plurality of groups of laminae,

a non-magnetic gap in each of said groups, said gaps being symmetrically distributed throughout the transverse and the longitudinal dimensions of said core.

1 3. A loading coil comprising a magnetic core, a plurality. of windings sectionally disposed thereon, said core having a plurality of partially transverse air-gaps symmetrically distributed with respect to said winding sections. I

1. A loading coil comprising a magnetic core, a plurality of windings sectionally disposed thereon, said core having a plurality of transverse partial air-gaps equal in number to a multiple of the number of said winding sections and symmetrically distributed with respect thereto.

In a loading coil, a magnetic core comprising a plurality of groups of annular laminae, a non-magnetic gap in each of said groups, said gaps being symmetncally positioned in said core, a plurality of windings completely covering said core and sectionally disposed thereon, said windings be ing equal in number to a multiple of the the two physical circuits and between the number of said gaps and symmetrically distributed with respect theretol In witness whereof, I hereunto subscribe my name this 18th day of November A. D.,

WILLIAM FONDILLER. Witnesses:

E. EDLER, K. L. STAHL.

Washington, D. G. 

